What are the rulings for silent "lām"s?

The silent lam (لْ) is divided into five categories: 1. The Lam of Definition (al): It is pronounced as a "moon letter lam" (lam qamariyyah) before 14 letters (أبغ حجك وخف عقيمه - abgh hajjaka wa khaf 'aqimah), and it is assimilated as a "sun letter lam" (lam shamsiyyah) before another 14 letters. 2. The Lam of the Verb: It is assimilated if followed by a lam (due to identical letters) or a ra (due to proximity), and it is pronounced clearly with other letters. 3. The Lam of the Particle (hal and bal): It is always pronounced clearly, unless followed by a lam (due to identical letters) or a ra (due to proximity). 4. The Lam of the Noun: It must always be pronounced clearly. 5. The Lam of Command: It must always be pronounced clearly.

For more details and exceptions, refer to books on Tajweed rules.